Secondary battery

Abstract

According to the present invention, a positive electrode is provided with: a positive electrode current collector; a positive electrode active material layer which contains a positive electrode active material that is configured from a lithium transition metal oxide; a protective layer which is arranged between the positive electrode current collector and the positive electrode active material layer; and a positive electrode tab which is bonded with the positive electrode current collector at a positive electrode tab bonding part where the positive electrode active material layer and the protective layer are not formed so that the positive electrode current collector is exposed. An end edge of the positive electrode active material layer facing the positive electrode tab and an end edge of the protective layer facing the positive electrode tab are arranged in different positions in the longitudinal direction of the positive electrode.

The invention claimed is: 
     
       1. A secondary battery, comprising:
 a positive electrode; 
 a negative electrode; and 
 an electrolyte, wherein 
 the positive electrode comprises:
 a positive electrode collector; 
 a positive electrode active material layer including a positive electrode active material composed of a lithium transition metal oxide; 
 a protective layer provided between the positive electrode collector and the positive electrode active material layer; and 
 a positive electrode tab bonded to the positive electrode collector at a positive electrode tab bonding part where the positive electrode active material layer and the protective layer are not formed and the positive electrode collector is exposed, and 
 
 an edge of the positive electrode active material layer which faces the positive electrode tab and an edge of the protective layer which faces the positive electrode tab are each disposed at a different position in a longitudinal direction of the positive electrode. 
 
     
     
       2. The secondary battery according to  claim 1 , wherein a distance between the positive electrode tab and the edge of the positive electrode active material layer is shorter than a distance between the positive electrode tab and the edge of the protective layer. 
     
     
       3. The secondary battery according to  claim 1 , wherein a distance between the positive electrode tab and the edge of the protective layer is shorter than a distance between the positive electrode tab and the edge of the positive electrode active material layer. 
     
     
       4. The secondary battery according to  claim 1 , wherein the protective layer includes an inorganic compound being at least one selected from a group consisting of metal oxides, metal hydroxides, metal carbides, metal nitrides, and metal borides. 
     
     
       5. The secondary battery according to  claim 1 , wherein the protective layer includes an electrical conductor and a binder. 
     
     
       6. The secondary battery according to  claim 1 , wherein a thickness of the protective layer is 1 μm or more and 5 μm or less. 
     
     
       7. The secondary battery according to  claim 1 , wherein the secondary battery is a cylindrically shaped secondary battery, and wherein an electrode assembly comprising the positive electrode, the negative electrode, and a separator is housed in a cylindrical battery case, and the positive electrode tab is welded to a sealing body included in the battery case. 
     
     
       8. A secondary battery, comprising:
 a positive electrode; 
 a negative electrode; and 
 an electrolyte, wherein 
 the positive electrode comprises:
 a positive electrode collector; 
 a positive electrode active material layer including a positive electrode active material composed of a lithium transition metal oxide; 
 a protective layer provided between the positive electrode collector and the positive electrode active material layer; 
 positive electrode tab bonding parts where the positive electrode active material layer and the protective layer are not formed and the positive electrode collector is exposed; and 
 a positive electrode tab bonded to the positive electrode collector at one of positive electrode tab bonding parts, 
 the positive electrode tab bonding parts comprises:
 positive electrode tab bonding parts form on each surface of the positive electrode current collector, 
 one of positive electrode tab bonding parts is provided on a side where the positive electrode tab is to be bonded to an area of the surface of the positive electrode current collector free of the positive electrode active material layer and the protective layer, and 
 the other positive electrode tab bonding parts is provided on a rear surface of the side where the positive electrode tab is to be bonded to the area of the surface of the positive electrode current collector free of the positive electrode active material layer and protective layer, 
 
 
 an edge of the positive electrode active material layer disposed on the rear surface and an edge of the protective layer disposed on the rear surface are each disposed at a different position in a longitudinal direction of the positive electrode. 
 
     
     
       9. The secondary battery according to  claim 8 , wherein a distance between the positive electrode tab and the edge of the positive electrode active material layer is shorter than a distance between the positive electrode tab and the edge of the protective layer. 
     
     
       10. The secondary battery according to  claim 8 , wherein a distance between the positive electrode tab and the edge of the protective layer is shorter than a distance between the positive electrode tab and the edge of the positive electrode active material layer. 
     
     
       11. The secondary battery according to  claim 8 , wherein the protective layer includes an inorganic compound being at least one selected from a group consisting of metal oxides, metal hydroxides, metal carbides, metal nitrides, and metal borides. 
     
     
       12. The secondary battery according to  claim 8 , wherein the protective layer includes an electrical conductor and a binder. 
     
     
       13. The secondary battery according to  claim 8 , wherein a thickness of the protective layer is 1 μm or more and 5 μm or less. 
     
     
       14. The secondary battery according to  claim 8 , wherein the secondary battery is a cylindrically shaped secondary battery, and wherein an electrode assembly comprising the positive electrode, the negative electrode, and a separator is housed in a cylindrical battery case, and the positive electrode tab is welded to a sealing body included in the battery case.